In satellite constellations, a number of satellites work together to provide coverage to a larger region than any of the satellites could cover on its own. For example, low Earth orbit (LEO) satellites can typically orbit the Earth at altitudes of around 100 miles with orbital periods of around 100 minutes, while geosynchronous satellites typically orbit the Earth at an altitudes of approximately 26,200 miles with an orbital period of approximately 24 hours (one sidereal day) to substantially match the Earth's rotation. Accordingly, LEO satellites can often operate with relatively higher link budget (e.g., due to the relative proximity of the satellite to the terrestrial terminals) and with a relatively low latency (e.g., around 1-4 milliseconds for a LEO satellite, as opposed to around 125 milliseconds for a geosynchronous satellite). However, the relative proximity of a LEO satellite to the Earth can also reduce its coverage area. Accordingly, a constellation of LEO satellites can be used to manifest a collectively increased coverage area, thereby allowing the satellites to service a larger region while exploiting the increased link budget and decreased latency provided by the lower orbit. A LEO constellation can result in the system capacity being thinly spread over the entire surface of the earth, with much of that capacity only available over the ocean where there may be relatively little demand.
For a group of LEO satellites to provide useful and economic communications services, a number of challenges are presented. For example, if communications beyond the range of a single satellite is desired, this can involve cross-links between multiple satellites of the constellation. Cross-links use additional power and mass on the spacecraft, and can thus be inefficient. Moreover, coordination of cross-links to ensure connectivity as the satellites move adds complexity. In order to maintain such cross-link, LEO satellite constellations are typically deployed with “processed” satellites, such that each satellite in the constellation includes its own, on-board processing for handling communications with terrestrial terminals and coordination with other satellites in the constellation. The processing involves de-modulating data communicated to the satellite on an uplink to allow the destination for the data to be determined. Then, the data is re-modulated and routed to the appropriate destination. This processing can add appreciable complexity, weight, and expense to the satellites.